where \(\mathbf {I}\)  denotes the diagonal matrix.
Besides, to further improve the performance, we refer to [1]}, introduce a self-training strategy to construct a more robust classifier.
That is, we use the \(\mathbf {W}\)  to classify the category of \(\mathbf {V}_{q}\)  by:
\(\begin{split}\mathbf {Y}_q =\mathbf {W} \mathbf {V}_{q}\end{split}\) 
